Factors Affecting Adsorption
Nature of adsorbent Same gas may be adsorbed to different extents on different adsorbent.
Surface area of the adsorbent Greater the surface area, greater is the extent of adsorption.
Nature of the gas being adsorbed Greater is the critical temperature of a gas, greater are the van der Waals’ forces of attraction and thus, greater is the adsorption.
Temperature Adsorption is an exothermic process involving the equilibrium Gas( adsorbate) + Solid( adsorbent) ⇔ Gas adsorbed on solid + Heat
Applying Le-Chatelier principle, increase of temperature decreases the adsorption and vice-versa.
Pressure Adsorption increases with pressure at constant temperature. The effect is large if temperature is kept constant at low value.
Activation of the solid adsorbent Activation means increasing the adsorbing power of the solid adsorbent. This can be done by subdividing the solid adsorbent or by removing the gases already adsorbed by passing superheated steam.
Adsorption Isotherms
It is the plot of the mass of gas adsorbed per gram of adsorbent( x / m) versus equilibrium pressure at constant temperature.